Method of forming the upper end of killed steel ingot



Aug 17, 1965 c. K. WERNER METHOD OF FORMING THE UPPER END OF KILLED STEEL INGOT 2 Sheets-Sheet l INVENTOR gar] if. PVerne-r Mi7m+ ATTOR m w ml l m Aug. 17, 1965 c.

METHOD OF FORMIN United States Patent 0 3,201,213 METHGI) @F FORMING THE UPPER END OF KILLED dTlEEL INGU'I Carl Kristian Werner, Vikrnanshyttan, Sweden, assignor to Uddeholms Aktiehoiag, Degeriors, Sweden, a Swedcorporation Filed Apr. 13, N59, Ser. No. 836,091 Claims priority, appiication Sweden, Dec. 1, 1955, 10,3'79/55 9 Claims. ((Il. 29-187) This application is a continuation-in-part of co-pending application Serial No. 624,325, filed November 26, 1956, and now abandoned.

This invention relates to the forming and rolling of metal ingots and more particularly to the forming of a cast steel ingot having a predetermined configuration such that when the ingot is rolled in accordance with the method of the invention the amount of unsound metal that must be cropped from the end of the resulting billet, or other article rolled from the ingot, is minimized. The invention is especially useful when employed in connection with the casting of killed or otherwise degasified steel ingots under a hot top which results in the formation of a sink head at the top of the ingot and will be illustratively described as used for this application. However, as the description proceeds it will become apparent that the invention can also be employed with advantage in connection with other processes for casting and rolling metals.

In the casting of killed steel ingots, the casting mold is ordinarily provided with a hot top, that is, a refractory-walled enclosure which has a diameter that is smaller than the diameter of the casting mold and which is adapted to contain a pool of molten metal that is in communication with the upper portion of the ingot being.

cast. As the cast ingot shrinks upon cooling, molten metal flows from this pool into the body portion of the mold and prevents the formation of shrinkage cavities in the ingot. Eventually the metal within the hot top solidifies to form at the top of the ingot an upwardly extending neck known as a sink head; If the hot top is properly made, the sink head formed therein can be cropped off to leave an ingot composed entirely of prime metal.

When an ingot from which the sink head has been cropped is rolled according to conventional practice, the outer portions of the ingot are elongated to a greater extent than the interior portions thereof. This differential elongation of the ingot causes the ingot ends to assume a funnel-shaped configuration, and the process by which the funnel-shaped ends are formed is commonly called fish-tailing. As rolling is continued the funnel configuration of the ingot end becomes continually deeper. This phenomenon will be discussed in more detail hereafter. For the present it will be suificient to point out that the fish-tails constitute unsound metal that must be cropped off and re-melted. Hence fish-tailing reduces the amount of sound metal that can be recovered from the ingot.

During the rolling operation the metal of the ingot being rolled is mechanically Worked and this mechanical working so alters the crystal structure of the cast metal as to produce a-significant improvement in the physical properties of the metal. In an effort to eliminate the fish-tailing problem, it has been previously proposed that the configuration of the cast ingot be modified in various ways. However, while the previously proposed ingot configurations have reduced fish-tailing to some extent, they have been subject to the disadvantage that they resulted in non-uniform mechanical working of the metal during rolling, and hence produced a variation in physical properties along the length of the rolled article.

It is accordingly an object of the present invention to provide an ingot configuration and method of rolling which minimizes the amount of metal that has to be cropped because of fish-tailing. It is another object of the invention to provide an ingot configuration such that during rolling the end portions of the ingot are worked to substantially the same extent as the middle portion of the ingot. Other objects of the invention will be in part obvious and in part pointed out hereafter.

In order to explain more fully the nature of the present invention, reference will now be made to the accompanyin g drawings wherein:

FIGURE 1 is a perspective view of a conventional cast killed steel ingot having the unsound top portion cropped 0d and having a test bolt mounted in the upper surface thereof;

FIGURE 2 is a section through the upper end of the ingot after it has been rolled to approximately one-fifth of its original transverse dimensions;

FIGURE 3 is a perspective view of an ingot formed in such manner as to include a beveled section between the sink head and body of the ingot according to the present invention;

FIGURE 4 is a vertical section taken on the line 44 of FIGURE 3 and further showing the configuration of the ingot; and

FIGURE 5 is a side elevation view of a modified form of ingot wherein the surface of the beveled section is curved.

FIGURES 6 and 7 are central longitudinal sections through ingots embodying the present invention and having configurations slightly'diflerent from the configurations of the ingots of FIGURES 3 and 5.

In order to demonstrate the effect of fis'h-taling in the rolling of a conventional ingot a test was made which is illustrated in FIGURES 1 and 2 of the drawings. Referring to FIGURE 1 there is shown an ingot 10 of killed steel weighing about 1075 kilograms and having a square cross-section which measures 0.41 meter on each side. Secured at the center of the upper surface 12 of ingot It there is a test bolt 14 having a composition substantially different from that of the body of the ingot so that it can be readily identified by sawing oh the end of the rolled billet.

The ingot of FIGURE 1 was rolled according to standard practice to reduce its transverse dimensions to about one-fifth of the original dimensions, specifically to 0.080 meter. The appearance of a longitudinal section through the rolled ingot is illustrated in FIGURE 2 of the drawings. From FIGURE 2 it is apparent that the exterior portions of the upper end of the ingot have been rolled over the central portion of the ingot to a considerable extent. More particularly, the top of the bolt 14 was found to be approximately 1.19 meters from the end of the rolled billet. This 1.19 meters represented unsound metal and had to be cropped from the billet and discarded. It weighed about 57 kilograms, that is, more than 5% of the weight of the original ingot.

It has been found that such excessive over-rolling or fish-taling can be substantially reduced by providing at the upper end of a killed steel ingot a beveled section having a predetermined bevel angle and having a length such as to give a predetermined reduction in the transverse dimensions of the ingot. Referring to FIGURES 3 and 4 the main body 16 of the ingot there shown merges at plane B into a frusto-pyramidal or beveled section 18 which in turn merges at plane A into the sink head 20. It has been found that both the bevel angle and the extent of convergence of the beveled section 18 should be kept within certain limits in order to achieve the desired results. The latter factor may be evaluated by dividing the transverse dimension of the ingot at plane A by the transverse dimension of the ingot at plane B and multiplying by 100 to obtain a precentage that is referred to in the present specification for convenience as the bevel ratio. The volumes of the metal in the sink head 20, beveled section 18 and body 16 are designated respectively as V V and V To achieve the objects of the present invention, it is important that the ingot be cast under a hot top to provide the three sections referred to above. If the beveled section 18 is to perform its proper function, it must be composed entirely of prime metal. Hence for the reasons indicated at the beginning of the present specification, the beveled section must be initially cast under a sink head which may be later cropped off.

As indicated above it is desirable both to minimize fish-tailing and to achieve substantially uniform working of the metal along the length of the billet during the rolling operation. Considering first the matter of reducing the fish-tailing effect, it has been found that substantial reduction in fish-tailing can be achieved by forming between the sink head 20 and the body 16 of the ingot a beveled section 18 having a bevel angle within the range 20 to 45 and a bevel ratio within the range 40% to 80%. The desired predetermined bevel angle and bevel ratio can be readily attained by casting the ingot under a hot top of the type disclosed in Tigerschiold application Serial No. 759,885, filed September 9, 1958. In accordance with this Tigerschiold application, an expansible template is introduced into the top of the casting mold and expanded to bring the lower edges of the template against the interior walls of the mold. The space between the template and mold walls is then filled with a hardenable mass of refractory material and the mass is hardened in place to form a hot top having a desired internal configuration, after which the template is collapsed and removed from the mold. By using a hot top formed in this manner ingots of the type illustrated in FIGURES 3 and 4 can be cast which have, between the sink head 20 and body 16 of the ingot, a beveled section "18 composed entirely of sound metal and having a predetermined bevel angle and bevel ratio within the ranges set forth above.

It is further desirable that the metal be worked in a substantially uniform manner along the length of the billet during the rolling operation, and it has been found that to achieve this objective a small but controlled amount of over-rolling should be employed. Referring to FIGURE 4, during the rolling operation the peripheral metal of the ingot at plane B moves toward the metal at plane A of the ingot, and as the rolling is continued the peripheral metal of plane B may approach the plane A metal, and more particularly the metal which, prior to rolling, was at center point C of plane A. For a given reduction in ingot diameter, the extent to which the peripheral metal at plane B approaches (or even passes) the metal at the center C of plane A is a function of the bevel angle and bevel ratio. Thus the desired controlled over-rolling for obtaining even working of the surface metal of the ingot can be achieved by proper selection of the bevel angle and bevel ratio.

The optimum bevel angle and bevel ratio for achieving the controlled over-rolling is somewhat different from the optimum bevel angle and bevel ratio for minimizing iis -tailing, but a good compromise is possible. Thus where it is desired to maximize the amount of substantially uniformly worked sound metal recovered from the ingot, the bevel angle should be maintained within the range 25 to 40 and the bevel ratio within the range 55% to 80%. By maintaining the bevel angle and bevel ratio within these relatively narrow limits the controlled over-rolling required for even working of the metal is obtained and at the same time a substantial reduction in the fish-tailing effect is achieved.

In order to illustrate the manner in which variations in the bevel angle and bevel ratio affect the extent to which over-rolling occurs, a number of tests have been made and data obtained in these tests are listed in the tables given below. The data in Table I were obtained 5 in tests wherein killed steel ingots of the big-end-up type Weighing about 1075 kilograms and having a square big end measuring 410 millimeters on the side at plane B were rolled to billets having a square cross-section measuring 80 millimeters on a side. The sink heads were cropped from the test ingots prior to beveling. The bevel top dimension listed in Table I is the transverse dimension of the ingot at plane A of the FIGURE 4 prior to rolling. The bevel ratio and bevel angle of Table I have been previously identified. In all cases the sink head was cropped from the ingot before rolling.

The last two columns of Table I list respectively the lengths of the ends of the rolled billet that had to be cropped to remove unsound metal and the weight of the crop in kilograms respectively.

Table I Bevel Top Bevel Bevel Length Wt. of Ingot No. Dimension Ratio, Angle of Crop, Crop,

percent mm. kgs.

Table II 40 Bevel Bevel Wt. of Ingot N 0. Angle Ratio, Crop, Remarks percent kgs.

0 100 20.38 Large fislrtails.

22 75 7. 91 Fish-tails. 25 40 3. 87 No fish-tails. 34 40 3. 06 D0. 24 1. 98 Very small fish-tails. 13 75 6. 38 Fish-tails. 14 60 5. 75 Very small fish-tails. 33 60 7. 23 Fish-tails. 40 40 3. (30 No fish-tails.

1 r-lz-is should be maintained between 0.08 and 0.18. By maintaining the relation between the sink head volume and the total volume of the ingot within this range, the amount .of metal in the sink head can be maintained relatively small without danger of forming shrinkage cavities in the bevel section 18.

In referring to the ingot of FIGURES 3 and 4, it was stated that the sink head 20 was removed from the ingot before rolling. However, it should be understood that the ingot can be rolled without first removing sink head 20 if desired. Also the beveled surfaces of section 18 need not be straight lines but may have curved surfaces such as the surface 22 of the ingot illustrated in FlGURE 5, provided that the line connecting the upper and lower edges of the curved surface (line D in FIGURE 5) conforms with the requirements for the bevel angle given above. Moreover, it should be noted that while the ingots of FIGURES l5 have been described as of square cross-section they may have round, rectangular, oval or other cross-sectional configurations as desired. Also although the ingots shown in the drawings have bevel sections only at their upper ends, the lower end of the ingot as well as the sides thereof may be beveled if desired, using bevel angles and bevel ratios within the ranges given above. Other modifications within the scope of the invention will be apparent to those skilled in the art.

From the foregoing discussion it should be apparent that the present invention provides a method and ingot capable of achieving the objects outlined at the beginning of the present specification. By selecting a bevel angle and bevel ratio Within the broader range disclosed and claimed herein, fish'ta ng can be substantially reduced. in those cases Where it IS important to insure working of the end portions of the billet to substantially the same extent as the central portion thereof, a controlled but small amount of over-rolling is desired. To achieve this more specific objective, it is desirable to select a bevel angle and bevel ratio within the narrower ranges disclosed above, namely, 25 to 40 for the bevel angle and 55% to 80% for the bevel ratio.

It is, of course, to be understood that the foregoing description is illustrative only and that numerous other modifications of the disclosed embodiments can be made which fall Within the scope of the invention as defined in the appended claims.

I claim:

1. A cast solid killed steel ingot adapted to be rolled to form a rolled billet bar of reduced cross-section, said ingot as cast comprising a body portion, a sink head at one end of said ingot, and an intermediate beveled section composed entirely of sound metal interconnecting said body portion and said sink head, said sink head including segregations of impurities and an unsound metal structure to be eliminated from said rolled billet bar, the surface of said beveled section forming with the central longitudinal axis of the ingot an angle of 20 to 45 and the length of said beveled section being such that the cross-sectional dimension of said ingot at the junction of said sink head and beveled section is from 40% to 80% of the corresponding cross ectional dimension at the junction of said body portion and said beveled section.

2. A cast solid killed steel ingot adapted to be rolled to produce an elongated billet bar of substantially reduced cross-section with substantially uniform working of the metal along the length of the resulting billet, said ingot as cast comprising a body portion, a sink head at one end of said ingot, and an intermediate beveled section composed entirely of sound metal interconnecting said body portion and said sink head, said sink head including segregations of impurities and an unsound metal structure to be eliminated from said rolled billet bar, the surface of said beveled section forming with the central longitudinal axis of the ingot an angle of 25 to 40 and the length of said beveled section being such that the cross-sectional dimension of said ingot at the junction of said sink head and beveled section is from 55% to 80% of the corresponding cross-sectional dimension at the junction of said body portion and said beveled section.

3. The method of making a rolled metal article which comprises casting an elongated solid killed steel ingot having a body portion, a sink head including segregations of impurities and an unsound metal structure to be eliminated from said metal article, and a beveled section composed entirely of sound metal interconnecting said body portion and sink head, the beveled surface of sai beveled section forming with the central longitudinal axis of the ingot an angle of 20 to 45 and the length of said beveled section being such that the cross-sectional dimensions of said ingot at the junction of said sink head and beveled section are from 40% to or" the corresponding cross sectional dimensions at the junction of said body portion and said beveled section, rolling said ingot to cause the metal forming the peripheral portion of the ingot at the junction of said body portion and beveled section to move axially toward the metal forming the junction between said sink head and beveled section, continuing the rolling of said ingot. until said peripheral metal is approximately aligned with the metal which, prior to rolling, was at the center of the junction plane between said sink head and beveled section, concentrating said segregations and unsound metal structure of said sink head into an extreme end portion only of said rolled metal article, and removing said extreme end portion from said rolled metal article.

4. The method of making a rolled metal billet bar which comprises casting an elongated solid killed steel ingot having a body portion, a sink head including segregations of impurities and an unsound metal structure to be eliminated from said rolled billet bar and a beveled section composed entirely of sound metal interconnecting said, body portion and sink head, the beveled surface of said beveled section forming with the central longitudinal axis of the ingot an angle of 25 to 40 the length of said beveled section being such that the cross-sectional dimensions of said ingot at the junction of said sink head and beveled section are from 55% to 80% of the corresponding cross-sectional dimensions at the junction of said body portion and said beveled section, rolling said ingot to cause the metal forming the peripheral portions of the junction of said body portion and beveled section to move axially outwardly toward the metal forming the junction of said beveled section and said sink head, continuing the rolling of said ingot until said peripheral metal is located slightly beyond the metal which, prior to rolling, was at the center or" the junction plane between said sink head and beveled section, concentrating said segregations and unsound metal structure of said sink head into an extreme end portion only of said rolled billet bar, and removing said extreme end portion from said rolled billet bar.

5. A cast solid killed steel ingot adapted to be rolled to form an elongated billet bar of reduced cross-section, said ingot as cast comprising a body portion, a sink head at one end of said ingot and an intermediate beveled section composed entirely of sound metal interconnecting said body portion and said sink head, said sink head includirn segregations of impurities and an unsound metal structure to be eliminated from said rolled billet bar, the surface of said beveled section forming with the central longitudinal axis of the ingot an angle of 20 to 45 and the length of said beveled section being such that the cross-sectional dimension of said ingot at the junction of said sink head and beveled section is from 40% to 80% of the corresponding cross-sectional dimen sion at the junction of said body portion and said beveled section, said body portion of said ingot being tapered and having its larger end adjacent to said beveled section.

6. The method of making a rolled metal article which comprises casting an elongated solid killed steel ingot having a body portion, a sink head including an unsound metal structure to be entirely eliminated from said metal article, and a beveled section composed entirely of sound metal interconnecting said body portion and sink head, the beveled surface or" said beveled section forming With the central longitudinal axis of the ingot an angle of 20 to 45 and the length of said beveled section being such that the cross-sectional dimensions of said ingot at the junction of said sink head and beveled section are from 40% to 80% or" the corresponding cross-sectional dimensions at the junction of said body portion and said beveled section, cropping said sink head and said unsound metal structure from said beveled section or" said solid ingot before the configuration of said ingot as cast is otherwise altered, then rolling said cropped ingot to cause the metal forming the peripheral portion of the ingot at the junction of said body portion and beveled section to move axially toward the metal forming the junction between said sink head and beveled section and continuing the rolling of said ingot until said peripheral metal is approximately aligned with the metal which, prior to rolling, was at the center of the junction plane I between said sink head and beveled section.

'7. The method of making a rolled metal article which comprises casting an elongated solid killed steel ingot having a body portion, a sink head including an unsound metal structure to be entirely eliminated from said metal article, and a beveled section composed entirely of sound metal interconnecting said body portion and sink head, the beveled surface of said beveled section forming with the central longitudinal axis of the ingot an angle of 25 to 40 and the length of said beveled section being such that the cross-sectional dimensions of said ingot at the junction of said sink head and beveled section are from 55% to 80% of the corresponding crosssectional dimensions at the junction of said body portion and said beveled section, cropping the sink head and said unsound metal structure from said beveled section of said solid ingot before the configurationof said ingot as cast is otherwise altered, then rolling said cropped ingot to cause the metal forming the peripheral portions of the junction of said body portion and beveled section to move axially outward toward the metal forming the junction of said beveled section and said sink head, and continuing the rolling of said ingot until said peripheral metal is located slightly beyond the metal which, prior to rolling, was at the center of the junction plane between said sink head and beveled section.

8. In a method for producing a cast killed steel ingot for rolling into an elongated billet bar of substantially smaller cross-section than said ingot and in which segregations of impurities form an unsound metal structure in a portion of said ingot during casting thereof, the steps which comprise casting molten steel to form said ingot into an upright casting mold, providing adjacent the top of said casting mold a hot top structure for maintaining a reservoir of molten metal above said ingot in said mold during solidification thereof for accumulating and concentrating said segregations and unsound metal structure into a distinct sink head portion on top of said ingot, forming on said ingot adjacent the top thereof and below said sink head portion beveled peripheral surfaces all around said ingot with said beveled surfaces forming an n an angle of about 20 to with the central longitudinal vertical axis of said ingot, the slant heights of said beveled surfaces being such that the cross-sectional area of a transverse plane through said ingot at the juncture between the upper edges of said beveled surfaces and said sink head is about 40% to of the cross-sectional area of a transverse plane through said ingot at the juncture of the lower edges of said beveled surfaces with the periphery of said ingot, said hot top being configured and disposed above said ingot to retain and concentrate substantially all said segregations and unsound metal structure in said sink head and substantially entirely above said beveled surfaces whereby the portion of said ingot defined by said beveled surfaces is composed substantially entirely of sound metal free of undesired impurities and segregations, removing said ingot as cast from said mold, and rolling said ingot into said billet bar with cropping of said unsound metal in said sink head portion substantially in the absence of wasting sound metal in the portion of said ingot defined by said beveled surfaces.

9. The method as recited in claim 1 in which said beveled surfaces are formed at the top of said ingot and below said sink head portion thereof by providing beveled casting surfaces at the bottom of said hot top and below said molten metal reservoir therein for molding said beveled surfaces on said ingot during said casting thereof in said mold.

References Cited by the Examiner UNITED STATES PATENTS 385,837 7/88 Boucher 22-147 1,055,833 3/13 Talbot 29-187 X 1,279,037 9/18 Talbot 22-147 1,581,512 4/26 Coates 29-187 X 2,010,650 8/35 Stone 29-552 2,021,227 11/35 Dornin 29-5266 2,030,199 2/36 Charman 22-147 2,282,462 5/42 Dornin 22-139 2,799,067 7/ 57 Peterson 22-147 2,903,762 9/59 Caudron 22-173 FOREIGN PATENTS 166,299 7/21 Great Britain.

OTHER REFERENCES Foundry, March 1956, pp. 128-135.

DAVID L. RECK, Primary Examiner.

NEDr/VICK BERGER, WHITMORE A. WILTZ,

ROGER L. CAMPBELL, Examiners. 

1. A CAST SOLID KILLED STEEL INGOT ADAPTED TO BE ROLLED TO FORM A ROLLED BILLET BAR OF REDUCED CROSS-SECTION, SAID INGOT AS CAST COMPRISING A BODY PORTION, A SINK HEAD AT ONE END OF SAID INGOT, AND AN INTERMEDIATE BEVELED SECTION COMPOSED ENTIRELY OF SOUND METAL INTERCNNECTING SAID BODY PORTION AND SAID SINK HEAD, SAID SINK HEAD INCLUDING SEGREATION OF IMPURITIES AND AN UNSOUND METAL STRUCTURE TO BE ELIMINATED FROM SAID RLLED BILLET BAR, THE SURFACE OF SAID BEVELED SECTION FORMING WITH THE CEN- 